Battery Analysis and Care (BACS) Battery Monitoring System

BACS is an advanced, 3rd generation battery management system.

Generex BACS BMS Connection Diagram

The system comprises of 4 main parts

Battery monitoring and equalisation

BACS battery monitoring module

A module is connected to each battery. It monitors for temperature and impedance, while actively adjusting the battery voltage to ensure the voltage is set at the UPS charger level. This process is called equalisation.

When actively monitoring and equalising batteries yields the following benefits

  • Avoiding over charging
  • Avoiding under charging
  • Avoiding sulfation
  • Detecting stratification
  • Detecting problems with the battery by monitoring temperature and impedance
  • Detecting and alerting to thermal runaway
  • increases battery life by 30%

Batteries supported

  • in VRLA, 16V, 12V, 6V and 2V
  • in NiCd, NiMH, and Lithium Ion from 1.2V – 3V

Monitoring and Reporting

BACS System status featuring battery string and number, voltage, temperature, impedance and equalisation

The BACS® WEB-MANAGER acts as the battery system‘s central control unit. It gathers, evaluates, and stores system information. The user is provided access to three web server pages. One displays the actual status of batteries; a second shows actual UPS data; the third shows environmental data and alarm contacts status. The web browser interface of the system is designed for easy configuration. It provides the user with access to all system values and events. A flexible programming interface known as the EVENT MANAGER coordinates a system response to significant events (alarms, notifications, etc.).

The WEB-MANAGER handles events involving the UPS, inverters, environmental sensors, transfer switches, generators, dry contacts, and other devices.


BACS® includes a full qualified UPS/SNMP and MODBUS manager, one that is compatible with any UPS presently on the market! Among BMS systems on the market, this function is unique.


BACS® allows MODBUS clients to read the system data through IP and RS232 (and, optionally, RS485), as well as through SNMP. Conversion to PROFBIS and LONBUS is possible through optional converters.


Provides graphical BACS® data analysis and reporting.

BACS View software stores battery voltage, impedance, temperature and discharge logs

Alerting and Warning System

BACS® has the ability to send out ―advance warning alarms via email, email-to-SMS, network message, SNMP, RCCMD, MODBUS, and, optionally, PROFIBUS, LONBUS, and GSM. (Alarm parameters can be configured by the user to match battery type.)

For instance, discovering rising internal resistance in a battery—an indicator of corrosion or sulfation— BACS® triggers an alarm.

Given early warning of issues, the user is able to investigate and take action far in advance of the consequences that can result from them. The effects of corrective actions taken are immediately observable. In addition to internal resistance, BACS® monitors voltage, temperature, the equalising process, the system‘s charging/discharging cycles, and, optionally, current. When pre-set thresholds of these categories are crossed, an alarm is communicated.

In addition to sending network alarms, BACS® also warns users via audible and visual signals (a buzzer on the BACS® MANAGER and alarm LEDs on the module and BACS® MANAGER).

UPS integration

BACS has the ability to integrate UPS monitoring and alerting via the serial port. Over 1400 UPS manufacturers are supported.

BACS battery management system (BMS) supports uninterruptible power supply (UPS) integration for monitoring, logging and alerts

Specifications and Standards

BACS system

BACS Webmanager BMS Controller
32-Bit RISC-processor
32 MB storage for battery history
Stabilized external power supply 12V 2000mA supplies 1830mA for up to 330 BACS C modules (@ 5mA) and other BACS bus sensors (See datasheet of other BACS sensors for power consumption)
3x RS-232 interfaces, (COM1= UPS/power device, COM2 =Multipurpose, service port for Windows BACS READER and PROGRAMMER software). 2x battery bus converter outputs internal. 1x RJ45, 10/100Mbit Ethernet. 1x potential-free contact (2 pole screw terminal for max. 1,0 mm², rated load 24 VDC /1A)
3x LED (Manager status, UPS/device alarm, BACS alarm). 1x Buzzer with mute button
Aluminium, RAL 7035 (light gray) ETL listed, FCC class A
130 x125 x 30mm = 5,12 x 4,92 x 1,18 in. (W x L x H)
Operating conditions MTBF (Calculated)
Temperature 0 - 60°C, max. humidity 90%, not condensing 70.000 hours (8 years)

BACS® modules (rev 3)

BACS Battery Module
Measuring modules with equalisation
BACS patent no.: DE 102004013351.4
Power consumption from battery
Consumption at normal operation: 15-20mA Consumption at “Sleep Mode” < 1mA
Measuring precision
Internal resistance : < 10 % at C40, < 5% at C20/30 Voltage : < 0.5 % Temperature: < 15 %
2x RJ10 for BACS battery bus Internal RS232 bus interface 1x button for the addressing Temperature sensor -35 to + 85 °C Optical display LED (alarms red/green, mode red/green)
ABS housing (UL certified, flame retardant, cooling fins)
55 x 80 x 24 mm = 2,17 x 3,15 x 0,94 in. (B x H x T), 45g
Operating conditions
Temperature 0 - 60°C, max. humidity 90%, not condensing IP 42 coated against dust and condensate)
High Voltage Tested
Protection against high ohmic batteries fault voltages up to 150 Volt /per module (fuse opens). At higher voltages the fuse opens, but BACS module is damaged. All REV 3.1 modules are designed for fault voltages up to 600 Volt
MTBF (calculated)
87,600 hours (10 years)

Models and Specifications

12V - BACS C20
REV 3 module for 12 Volt 7-600Ah lead batteries (UL certified)
Voltage Range
9.7V – 17V
RI Range
Equalisation Current
0.15 A
16V – BACS C23
REV 3 module for 16 Volt 7-600Ah lead batteries (UL certified)
Voltage Range
9.7V – 21V
RI Range
Equalisation Current
0.12 A
6V – BACS C30
REV 3 module for 6 Volt 7-900Ah lead batteries (UL certified)
Voltage Range
4.8V – 8V
RI Range
Equalisation Current
0.3 A
2V – BACS C40
REV 3 module for 2 Volt 7-5000Ah lead batteries, NiCd, NiMH batteries (UL certified)
Voltage Range
1.25V – 3.2V
RI Range
Equalisation Current
0.9 A (at 2.27V)

Options and Accessories

Current sensors

200A DC, 400A DC, 500A DC, 1000A DC, 1500A DC

BACS CS Current Transformer (CT)

SensorManager II – Adding additional sensors

Generex SensorManager


Generex Battery Management Datasheet
Click here to see more sensors